Just maintenance, since a lot of SEA players had connection issues yesterday night. Altho not officially released in SEA they did fix it rather quick.
Make an iTunes account for a different region.

Actually all units are good in this game. Well balanced game mostly. It's just up to your preference what units you find good, because each unit has different roles in the game because of their different skill sets. There is no bad operators, only bad doctors

Yeah Angelina isn't as good when starting out, but once she is invested and you get her to Elite 2, she is one hella a beast in game. Instead of focusing on just playing higher rarity operators, I suggest you to use those free operators as well since they are good.

buncha 2* - 4* unit can take you far , especially after E1 them

my recommend
Defender - Beagle, Cuora, Noir Corne, Gummy
Vanguard - Courier,Vanilla, Scavenger, Fang, Yato, Vigna
Guard - Melantha, Plume
Sniper - Jessica, Kroos, Rangers, Adnachiel
Aoe Sniper - Catapult, Shirayuki
Aoe Caster - Lava, Gitano, 12F
Aoe Healer - Gavial, Perfumer
Healer - Ansel, Hibiscus, Lancet-2
Specialist ( important role in Annihilation mode ) - Shaw, Cliffheart

Bolded name is highly recommend you to raise first

Cuora can be brought from shop
Gavial and Courier is shop exclusive ? correct me if im wrong.
can instant hire Gummy if you spend Starter Pack around 1USD. very tanky tank since she can heal herself.